LLVM should be target independent because it will work with all
machine types. This is different from GCC where it needs to know what
target to build ahead of time.
This makes LLVM tools (including dependent tools such as LLD) readily useful in
more situations, foresees such needed additions as BPF and NVPTX, and brings
llvm_6 and newer on par with the current default llvm_5.
* add generic x86_32 support
- Add support for i386-i586.
- Add `isx86_32` predicate that can replace most uses of `isi686`.
- `isi686` is reinterpreted to mean "exactly i686 arch, and not say i585 or i386".
- This branch was used to build working i586 kernel running on i586 hardware.
* revert `isi[345]86`, remove dead code
- Remove changes to dead code in `doubles.nix` and `for-meta.nix`.
- Remove `isi[345]86` predicates since other cpu families don't have specific model predicates.
* remove i386-linux since linux not supported on that cpu
LLVM’s `LLVM_TARGETS_TO_BUILD` build flag defauls to `all`, which contains
`AMDGPU` among others. [1] Changes in llvm [2] switched to explicitly listing
host and target platforms, excluding the AMDGPU target, which is required
for Mesa to build.
[1]: db50b6fe39/CMakeLists.txt (L286-L302)
[2]: https://github.com/NixOS/nixpkgs/pull/52031
